Functions allowing forms processing to be spread out over several page
requests, thus ensuring that the processing does not get interrupted
because of a PHP timeout, while allowing the user to receive feedback
on the progress of the ongoing operations.

The API is primarily designed to integrate nicely with the Form API
workflow, but can also be used by non-Form API scripts (like update.php)
or even simple page callbacks (which should probably be used sparingly).

Comments

I try to set a cron in linux crontab with wget but my batch URL don't work with wget and lynx. If I click it on browser it works fine but when I call from command line it's not working. Is there a way to call a batch script from crontab?

With wget or lynx, you usually make one request at all. However, batch processing requires multiple sequential requests to be finished at the end. With your browser it works fine because the browser does the subsequent requests for you, either via AJAX when Javascript is enabled or per HTML meta tags to let your browser know when and which request should be performed next. For the cronjob, you'll need to implement a script which reads the meta tags from the HTML code and does the subsequent requests after a specified amount of time. Alternatively you could look for a headless browser or something which is able to handle this for you.